For those of us who aren't good at keeping password, If you've lost your password - you can only access your account after resetting the password. See How to Change Facebook Password.
Reset tells Facebook to forget about the lost password but rather send you a new reset code. Usually the Facebook reset code is sent to the mobile number associated with your Facebook account.

Keep in mind that Reset is different from changing password on Facebook. If you have your password - what you should do is to change your password. This is more straight forward because you'll not be asked too many security questions to prove ownership of the account.